1. Field of the Invention
The present invention relates generally to systems for transmitting and receiving information, and more particularly, to antenna systems for transmitting and receiving signals using electronic beam forming. Exemplary embodiments are applicable to any situation where antennae are used including, but not limited to, any communication systems that involve wireless transmission or reception of signals.
2. Background Information
Antenna systems for transmitting and receiving information are used for a variety of applications, including wireless communication system applications and radar applications which involve object detection and tracking. These antenna systems are typically configured to accommodate the sequential channel processing associated with low cost radio frequency (RF) seeker applications (that is, object detection and tracking), among other radar applications.
A typical antenna system suitable for these radar applications is a cassegrain antenna system, wherein the antenna includes multiple output ports. A conventional cassegrain antenna system also includes waveguide material, known in the art as a "magic T", to passively (that is, without electronic components) provide multiple antenna system outputs. For example, a typical four channel cassegrain antenna supplies A, B, C and D signals from the antenna output ports to the waveguide material of the antenna system. The waveguide material can be a plurality of magic T's. The waveguide material includes a plurality of antenna system ports, which can provide or receive the variety of signals that are of interest to various applications for which the antenna is to be used.
For example, output signals from the waveguide material can include a summed output signal: A+B+C+D, and a differential output signal: A+B-C-D or A+C-B-D. The summed output signal and the differential output signal can be combined in a transceiver to provide, for example, monopulse indications of the azimuth and elevation of an object to be detected and/or tracked.
Because the cassegrain antenna system uses waveguide material to produce output signals of interest at a plurality of separate antenna system ports, a transceiver which receives the signals to produce the azimuth and elevation information, or which supplies signals to the antenna, must be configured as a multichannel transceiver. The transceiver must have a separate channel for each port of the antenna system's waveguide material to provide the desired active and passive tracking functions for which the antenna system is to be used. These multichannel transceivers are complex and costly because of the active components they require to provide the multichannel functionality. Moreover, each of the multichannel paths in the transceiver must be calibrated independently, and repeatedly recalibrated to ensure accurate, reliable operation, thus adding to the cost and complexity of the transceiver.
Accordingly, it would be desirable to provide an antenna system for receiving and transmitting signals which is suitable for a variety of applications including, but not limited to, communication systems and radar systems, but which does not require the associated transmitter, receiver or transceiver to possess the hardware, high cost and circuit complexity of conventional systems.